a. Field of the Invention
The invention relates to radiopaque polymer compositions for use in medical and surgical devices. The polymer compositions have improved melt processability along with balanced or enhanced physical and mechanical properties, especially when combined with or over-extruded onto or covering other polymer layers, such as soft and/or flexible layers commonly used in medical device applications and catheter tips, for example. The ability to incorporate radiopaque components allows improved methods for monitoring and visualizing medical devices when used inside the body and improves the operating characteristics of the medical device components.
b. Background and Introduction to Invention
A growing number of surgical or medical procedures employ devices and kits that rely on inserting a device, catheter, or tube into the body and visualizing the placement or movement of the device and/or its progress during a procedure. There is an increasing need for developing radiopaque polymer compounds that can be used for high performance catheter shafts employed in these procedures. However, radiopaque compounds must be chemically compatible with the thermoplastic elastomer or other polymer selected for the flexible and soft medical devices or parts thereof, such as catheter tips. For example, the catheter tip materials can be composed of soft, polyamide-based thermoplastic elastomers, polyester-based thermoplastic elastomers, thermoplastic polyurethanes, or silicone-thermoplastic polyurethanes having low durometers ranging from 25 D to 55 D. These soft polymer materials may not have significant radiopaque properties and more undesirably, they are largely lacking in the sufficient mechanical strength properties required for making the slender body of a catheter shaft, for example.
Polycarbonate (PC) resins are widely used and commercially available. PC resins are selected primarily due to their superb material toughness, thermal stability, and excellent mechanical strength. However, polycarbonate has limited chemical resistance and is characterized by a rapid solidification during melt processing due to its amorphous nature. The latter property may make it difficult to over-extrude PC on other layers by melt processing. Also, high performance polycarbonate resins generally have high viscosity due to high molecular weights, and generally have to be extrusion-processed at temperatures as high as 270° C., even up to 300° C. This imposes limitations on the types of processes and products that can be manufactured from PC in combination with other polymer materials having lower melt processing temperatures. Therefore, a number of limitations exist in using pure PC resins for medical and surgical devices.
Accordingly, in one aspect, the invention addresses the need for radiopaque polymers that can be used in medical and surgical devices. In another aspect, the invention addresses the need for polycarbonate resins that can be modified for use as a high-performance polymer in medical and surgical devices and methods. As explained more fully below, the polymer compositions of the invention improve the melt processability of polycarbonate resin along with various enhancements in physical and mechanical performance when used for a variety of medical and surgical devices and kits. In addition, the polymer compositions of the invention can be used to improve the X-ray radiopacity, namely the ability to visualize basic catheter and medical device parts or elements in the human body.